Field of the Invention
The present invention relates to a hydraulic-pressure generator.
Description of the Related Art
A widely known hydraulic-pressure generator for a vehicle brake system includes a master cylinder in which two pistons are displaced by tread force with which a brake pedal is depressed, hydraulic pressure corresponding to the displacement of each piston is generated in the master cylinder, and the generated hydraulic pressures are supplied to hydraulic paths in two hydraulic routes. In the master cylinder in the above hydraulic-pressure generator, two pressure chambers realized by the two pistons and a cylinder tube enclosing the two pistons generate the hydraulic pressures, and rapid variations in the hydraulic pressures can cause slight turbulence in the rate of displacement of the brake pedal, and cause the driver to feel a sense of incongruity which deteriorates the brake feel (pedal feel). Therefore, it is desirable to suppress the above turbulence in the rate of displacement of the brake pedal. For example, International Patent Publication WO2010/137059 discloses a technique for improving the pedal feel when the brake pedal is depressed. The improvement is made by causing port openings (communication openings) provided for releasing the hydraulic pressures of two pressure chambers to open at different timings.
However, WO2010/137059 does not disclose a technique for reducing turbulence in the rate of displacement of the brake pedal when the brake pedal returns from a depressed state, although WO2010/137059 discloses the technique for improving the pedal feel when the brake pedal is depressed.
In view of above, the object of the present invention is to provide a hydraulic-pressure generator which can improve the brake feel when the brake pedal returns from a depressed state.